1. Field of the Invention
The present invention relates to an apparatus and a method for receiving a multiple Frequency Allocation (FA) for a mobile communication terminal in a mobile communication system.
2. Description of the Related Art
In an Institute of Electrical and Electronics Engineers (IEEE) wireless Metropolitan Area Network (MAN) system, a Frequency Overlay function is required for simultaneously supporting terminals having different bandwidths of the same frequency band.
FIG. 1 is a view illustrating a frequency overlay system that simultaneously supports two terminals using a frequency bandwidth of 20 MHz when a 10 MHz-terminal and a 20 MHz-terminal coexist simultaneously.
Referring to FIG. 1, to support a frequency overlay function, a narrow band terminal (10 MHz) 110 uses a narrow band (10 MHz) FA, and a broadband terminal (20 MHz) 120 uses a broadband (20 MHz) using a plurality of narrow band (10 MHz) FAs (that is, two narrow bands for a 20 MHz-system).
An International Mobile Telecommunication (IMT)-advanced system requires different FA depending on a nation and a company, and an IEEE 802.16m system supports a scalable bandwidth ranging from 5 MHz to 40 MHz. This may be realized via transmission/reception of a single carrier or a multiple radio frequency carrier.
FIG. 2 is a view illustrating a system where a 20 MHz-terminal uses two bandwidths of 10 MHz.
Referring to FIG. 2, a 20-MHz terminal 210 that supports a multiple RF carrier uses two bandwidths of 10 MHz.
In this case, it is easy for base station equipment to use a single broadband transmitter/receiver for transmission to a plurality of terminals via a plurality of frequency channels. However, it is more reasonable that a terminal uses one narrowband transceiver or a plurality of narrowband transceivers having the same bandwidth as a legacy system due to hardware complexity and backward compatibility.
An IEEE 802.16m communication system may use a multiple carrier in order to improve a data transmission rate and support a specific service. Here, a carrier that a terminal accesses via synchronization and an access is called a primary carrier, and an additional carrier is called a secondary carrier.
In an IEEE 802.16m communication system, a primary carrier and a secondary carrier may be allocated to a contiguous spectrum or a non-contiguous spectrum. In addition, whether a terminal supports a multiple carrier may be determined by message exchange between a base station and a terminal.
To receive two contiguous FA using a double RF chain terminal, respective RF chains are used when data is received in contiguous frequency channels (for example, frequency channels #2 and #3). In addition, a center frequency of a mixer is set to frequencies of frequency channels #2 and #3, so that a baseband signal is processed.
Since a double RF chain terminal receives two frequency channels via respective RF chains, a signal RF chain receiver structure is further required additionally, and a related analog device (that is, an external Low Noise Amplifier (LNA), an Analog to Digital Converter (ADC)), etc. are additionally used. In addition, since a double RF chain structure uses an independent RF chain with respect to each FA, RF gain control is easy but consumes two times more analog device power than a single RF chain structure.
That is, in the case where an independent RF chain and an analog device are used for receiving a multiple carrier, power consumption by RF chains and analog devices increased as much as the number of simultaneously supported carriers is large.
Therefore, an apparatus and a method for receiving a multiple carrier using one RF chain are required.